An amazing light show appeared, faded, then reappeared in greater glory along I-89 in the general area of Grantham, NH yesterday morning.
Jann and I were “car pooling”—I had an assignment to photograph a yoga teacher, and Jann would drop off a quilt to be quilted in Newport on the way home. Jann first noticed a single sun dog. She made a few photos through a very dirty window made worst by the glare of the brilliant sun. I pulled over made a few quick photos and then we resumed our drive as the sun dog faded. I feared being late—I needed to meet and talk with the instructor before class started.
But the show was far from over—now there were a pair of dogs (bright spots on each side of the sun at the elevation of the sun) as well as a faint 22 degree halo through them. I pulled over again and shot a series of photos at varying exposures. I wish I would have had time to change to a wider lens than the 18mm on my D300. But we are thankful that we could witness the celestial show on a brilliant, below zero degree Fahrenheit morning.
From “Kaleidoscope Sky” by Tim Herd, a 22 degree halo is produced by the refraction of light through faces of ice crystals. The light from the cloud of falling crystals “is deviated a minimum of about 22 degrees, varying slightly according to wavelength, to create a ring of color about 22 degree from the Sun or Moon, with red on the inside. Some rays bend at greater angles and account for the fading, outward edge of the halo extending up to 50 degrees. No light is bent less than 22 degrees, which creates the halo’s dark center.”
The vertical flare extending above and below the sun is a sun pillar, also caused by falling ice crystals. I do not yet understand the narrow circular arc at the edges of the photo. Perhaps it is caused by an optical effect in the lens. I admit I did not notice it when I took the photos–but I was in a hurry and cars were whizzing by, in spite of the fact that the road looks empty in this photo.
Optical shows in the sky can be spectacular. Jann and I were fortunate enough to witness an amazing show in Carefree Arizona April 16, 2009. It happened around noon and lasted over an hour. Here is a 22 degree halo below the sun and a circumhorizontal arc below the halo. 
Here is a piece of the circumhorizontal arc. It is also caused by ice crystals in the sky.
This photo shows what we referred to as the stairway to heaven—clouds leading to the arc.
A bit over a month after that show in Arizona, I rode my mountain bike into Cherry Pond in NH to photograph the sunrise. I was treated to a double sun dog show over the pond as shown below.